1. Back pressure turbine is placed between ____________
a) Turbine & Pump
b) Boiler & Pump
c) Turbine & Heat Exchanger
d) Boiler & Turbine
Explanation: In a cogeneration plant, the back pressure turbine is placed between the boiler & turbine.
2. Which of the following is a good medium for constant temperature heating?
a) Water
b) Steam
c) Coolant
d) Diesel
Explanation: For constant temperature heating (or drying), steam is a very good medium since isothermal condition can be maintained by allowing saturated steam to condense at that temperature and utilising the latent heat released for heating purposes.
3. The cogeneration plant efficiency nCO if WT, Qi, QH represents turbine work, heat input, heat output respectively is given by?
a) nCO = (WT + Qi) / QH
b) nCO = (WT – Qi) / QH
c) nCO = (WT + QH) / Qi
d) nCO = (WT + QH) / Qi
Explanation: The cogeneration plant efficiency nCO if WT, Qi, QH represents turbine work, heat input, heat output respectively is,
nCO = (WT + QH) / Qi.
4. The electricity fraction of total energy output if W1 and Q1 represents the turbine work and heat output is given by?
a) W1 / (W1 + Q1)
b) W1 / (W1 – Q1)
c) W1 / (W1Q1)
d) W1 / Q1
Explanation: The electricity fraction of total energy output if W1 and Q1 represents the turbine work and heat output is,
W1 / (W1 + Q1).
5. If e is the electricity fraction of the total energy output, m is the electric plant efficiency and n is the steam generator efficiency; the heat added per unit total energy output is given by?
a) (1 / m) + ((1 – e) / n)
b) (1 / n) + ((1 – e) / m)
c) (1 / m) + ((1 + e) / n)
d) (1 / n) + ((1 – e) / m)
Explanation: If e is the electricity fraction of the total energy output, m is the electric plant efficiency and n is the steam generator efficiency; the heat added per unit total energy output is given by?
(1 / m) + ((1 – e) / n).
6. Pass-out turbines are used in which of these cases?
a) relatively high back pressure
b) small heating requirement
c) only relatively low back pressure
d) both relatively high back pressure and small heating requirement
Explanation: Pass-out turbines are used in cases of relatively high back pressure and small heating requirements. They are used in cases where a certain quantity of steam is continuously extracted from the turbine at an intermediate stage for heating purposes at the desired temperature and pressure.
7. Which of these is not considered economical for cogeneration?
a) a high fraction of electric to total energy
b) a low fraction of electric to total energy
c) a low fraction of total energy to electric energy
d) none of the mentioned
Explanation: A low fraction of electric to total energy is considered as an economical condition for cogeneration. Cogeneration plant is defined as a plant which produces electrical power and processes heat simultaneously.
8. Addition of an infinitesimal amount of heat at the highest temperature is because ___________
a) to initiate reheating
b) to initiate regeneration
c) to initiate superheating
d) none of the mentioned
Explanation: The maximum temperature gained in steam cycles using the best available material is about 600 degree Celsius while the critical temperature of steam is about 375 degree Celsius, which necessitates large superheating and permits addition of an infinitesimal amount of heat at the highest temperature.
9. High moisture content is involved during expansion of steam because ___________
a) to ensure uniform heating
b) to ensure uniform cooling
c) to obtain a higher temperature of heat addition
d) to obtain a lower temperature of heat addition
Explanation: In order to obtain a higher temperature of heat addition, heat moisture content is involved during expansion of steam.
10. What is the relation of the mean temperature of heat addition and cycle efficiency?
a) both are inversely proportional
b) both are directly proportional
c) both are independent of each other
d) none of the mentioned
Explanation: The cycle efficiency is a function of mean temperature of heat addition. Hence, both are directly proportional to each other. The need for high pressure is only forced due to weak characteristics of steam.